This invention relates to electrical measurements and more particularly to improved method and means for measuring the level of electromagnetic emission emanating, for example, from electrical apparatus under test operating in the RF frequency range.
Electromagnetic interference is generally defined as any electrical disturbance which causes an undesirable response or malfunction in any electronic apparatus. The interference energy can be either radiated or conducted. Radiated interference, however, constitutes a major problem due to the large number and kinds of electronic and electromagnetic apparatus that often must be grouped together in a relatively small area such as on a plane or vessel, a communication center, and a control center or the like. Any electrical, electronic or electromagnetic apparatus is adapted to generate some type of interference emission which operates to decrease the reliability efficiency and accuracy of other apparatus operating in the locality.
In order to design electronic apparatus that is not a source of and/or susceptible to undesirable interference, particularly in the form of radiation, there must be adequate means for measuring this interference. In the past, measurements had to be made which involved a complicated and laboriously time consuming procedure which were inherently inaccurate. One attempt to provide a more reliable means of making reliable interference measurements is disclosed in U.S. Pat. No. 2,952,768 entitled, "Automatic Peak Level Indicator System", which issued on Sept. 13, 1960 to H. R. Caler, et al. The circuitry described in the Caler patent involves a superheterodyne circuit having a gain control and a manually continuously adjustable frequency tuning control and a peak level indicator circuit coupled to the output of the superheterodyne circuit. While such apparatus provided an improvement over the then existing prior art, certain limitations still present themselves, namely the need for manual tuning and/or scanning.
It is an object of the present invention, therefore, to provide improved means of making emission measurements of electromagnetic energy.
It is another object of the present invention to make emission measurements of undesirable radio frequency interference over a relatively wide bandwidth without the necessity of tuning or scanning.
Still another object of the present invention is to provide a one-shot measurement of undesirable emission without the knowledge of a specific signal characteristic of the emission.
And still a further object of the present invention is to provide a measurement of electromagnetic emission on a go/no-go basis.